Various types of high temperature packers have been devised, including those disclosed in U.S. Pat. Nos. 6,481,497, 6,318,460, 6,102,117, 5,433,269, 5,311,938, 4,709,758, 4,665,978, 4,584,264, 4,479,369, and 4,296,806. U.S. Pat. No. 6,406,028 discloses a seal stack, and U.S. Pat. No. 6,915,856 discloses a technique for preventing axial movements of downhole tool assemblies.
While the components of a downhole packer may be manufactured for operation at a certain temperature, a significant problem concerning reliable operation of downhole packers involves the packer being axially mounted on a tubular string, which may then be expanded to engage and seal with casing string or the borehole. As the temperature fluctuates considerably downhole due to downhole conditions, thermal expansion and contraction of the tubular string places a high axial force on the packer body, which may result in destruction of the packer sealing elements. One of the techniques to avoid this destructive behavior is to provide a mechanism which axially releases the packer body from a central mandrel, so that elongation and contraction of the tubular string would not adversely affect the packer. U.S. Pat. No. 4,176,715 discloses such a releasing mechanism, and U.S. Pat. Nos. 4,709,758 and 4,730,760 disclose slick joint portions within the packer body, so that axial movement of the tubing string in either direction relative to the set packers is possible.
One of the problems with the above devices is that the packer body is preferably secured at a fixed axial position when run in the well, so that the depth of the set packer will be known. The packer body once set may be released from the tubular string to accommodate thermal expansion, but this operation requires that the operator perform these steps to release from the set packer. This packer releasing operation must be performed reliably and with a minimal of time and expense. Packer bodies which are provided on a slick joint can readily move axially along the slick joint if they are not set in initial position. The position of the packer body relative to the slick joint determines whether the necessary expansion and contraction stroke are able to be achieved before the packer head “tops out” or “bottoms out” with no further stroke possible.
The disadvantages of the prior art are overcome by the present invention and an improved high temperature packer and method are hereinafter disclosed.